Hemostasis is the means by which blood loss is terminated from an injured artery, vein, or damaged parenchyma. The process of hemostasis uses circulating proteins such as coagulation factors, cell membranes, and the lining of the blood vessels called endothelium. Hemostasis as a process is highly complex, begins with vasoconstriction, local mediators, platelet adherence to the vessel wall, aggregation of platelets, and the release of platelet granules. At the same time, the coagulation cascade is triggered with the two traditional divisions of the coagulation process—the intrinsic and extrinsic pathway processes that are measured by clotting time. Ultimately these processes lead to blood clotting which, along with platelet aggregation, seal the injured artery or vein.
Following trauma, such as may be recognized in military medical care or traditional civilian trauma, the physician must identify all sources of blood loss from the patient such as the skin surface, thorax, abdomen, pelvis or retroperitoneum, and fractured limbs or skull. Often traumatized patients also suffer from complications such as hypotension, acidosis, hypothermia, organ dysfunction and severe shock. Under such conditions, rapid hemostasis is critical and must begin even before blood transfusion is available. Accordingly, topical and implanted hemostatic agents have gained importance in all causes of trauma including trauma in the military field.
Surgical intervention due to diseased or damaged tissues such as the surgical excision or removal of tissue can result in blood loss due to severed vessels. Current standard of care includes thermal coagulation and closure of the vessels and tissue which can result in thermal damage to the site and surrounding tissues and impede repair and function. Achieving non-thermal hemostasis at a surgical site in a patient could result in improved healing outcomes.
The properties of an ideal topical hemostatic agent include rapid hemostasis, easy application both internally and externally, suture strength, bioresorption, manipulability, minimal adverse tissue reaction, long shelf-life, and low cost. Pusateri et al. Making sense of the preclinical literature on advanced hemostatic products. J Trauma 60(3): 674-82 (2006). An additional desirable characteristic of a hemostatic device is that it has anti-microbial properties.
Numerous topical hemostatic agents have been developed but all of these agents have substantial drawbacks. Although the last decade has been a turning point in the treatment of acute traumatic hemorrhage with the advent of several new hemostatic dressings, an unacceptably high proportion of pre-evacuation combat deaths in Operation Iraqi Freedom and Operation Enduring Freedom are attributed to uncontrolled hemorrhage. Emergency Medicine Review: 2005, p. 1-4. These currently deployed technologies have persistent problems: QuikClot zeolite granular dressing (QC, Z-Medica) can cause exothermic reaction at the application site (J. Trauma, 2008. 64(4): p. 1093-9) and may be ineffective in bleeding fields; chitosan hemostatic dressing (HC, Hemcon) and Rapid Deployment Hemostat (RDH, Marine Polymer Technologies) are non-bioabsorbable, J. Trauma, 2006. 60(3): p. 674-82. None of these dressings are currently FDA cleared for internal use. Collagen sponges, and gelatin sponges may not result in enhanced platelet aggregation and may not have a significant impact on clotting time. The potentially implantable dry fibrin sealant dressing (DFSD, American Red Cross) is expensive, regulated as a biologic, and is currently only approved for investigational use. None of the current topical hemostatic agents are believed to have antimicrobial properties.
Urinary bladder matrix (UBM) is a well-characterized scaffold that was developed for site-specific tissue repair of various tissues and was found to have anti-microbial in vitro as well as regenerative properties.
UBM is derived from the extracellular matrix of the urinary bladder of pigs. Other animals, such as ruminants, are also suitable sources of UBM. UBM, in contrast to other ECMs, includes the epithelial basement membrane and other layers of the wall of the urinary bladder and is composed of at least collagen types I-IV and VII. Collagen VII is specifically of epithelial basement membrane origin. Other components of UBM of porcine origin include glycosaminoglycans, fibronectin, laminin, elastin, and the following growth factors: vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2), and connective tissue growth factor (CTGF). K A Kentner & A D Janis, Quantification of FGF-2, VEGF, & GAGs in MatriStem MicroMatrix UBM Biomaterial. BMES 2011 Fall Meeting, Hartford, Conn., Oct. 12-15, 2011. K A Kentner, K A Stuart & A D Janis. Differential release of growth factor from MatriStem® urinary bladder matrix (UBM) products. Society for Biomaterials 2012 Fall Symposium, New Orleans La., Oct. 4-6, 2012. A C Phipps, K A Kentner, K A Stuart, B T Kibalo and A D Janis. Tunable mechanical, structural and biological properties of urinary bladder matrix (UBM) biomaterials. BMES Annual Fall Meeting, Atlanta, Ga., Oct. 24-27, 2012.
Extensive preclinical studies have demonstrated the efficacy of UBM in a wide range of applications, including myocardial repair, esophageal reconstruction, thoracic wall repair, urinary incontinence, penile tunics repair, orthopedics, amputated digit remodeling, and tympanoplasty. UBM was observed to gradually be replaced with implant site-appropriate host tissue following infiltration of the UBM implant by progenitor cells (Tissue Eng. Part A. 2009. 15(5): p. 1119-25), a mechanism of action that has been well characterized in studies of similar ECM-derived scaffolds in vivo. Degradation products of UBM have been demonstrated to have antibacterial activity in vitro (Tissue Eng. 2002. 8(1) p. 63-71; Tissue Eng. 2006. 12(10): p. 2949-55) and in vivo. Medberry et al., J. Surg. Res. 2010.
UBM (MatriStem®, ACell Inc., Columbia Md.) was FDA cleared in 2002 as a medical device and is currently marketed for indications ranging from topical use in cutaneous wounds (J. Am. Coll. Cert. Wound Spec. 2010. 2(3): p. 55-69) and burns to implanted plastic and hernia surgery repair. Wound Repair. Regen. 2011. 19: p. A54, UBM is currently commercially available as powder, lyophilized sheets, and vacuum-pressed multilaminate sheets, and proof of concept gel formulations of ECM have been described. Biomaterials. 2008. 29(11): p. 1630-7; Tissue Eng. 1998, 4(2): p. 157-174.